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by linearly reducing feather damage. Providing diluted rearing diets increased feed intake from the first weeks of life onwards. It was hypothesized that pullets ...
METABOLISM AND NUTRITION Effects of nutrient dilution and nonstarch polysaccharide concentration in rearing and laying diets on eating behavior and feather damage of rearing and laying hens M. M. van Krimpen,*1 R. P. Kwakkel,† C. M. C. van der Peet-Schwering,* L. A. den Hartog,†‡ and M. W. A. Verstegen‡ *Animal Production, Animal Sciences Group, Wageningen UR, PO Box 65, NL-8200 AB Lelystad, the Netherlands; †Animal Nutrition Group, Department of Animal Sciences, Wageningen University, PO Box 338, NL-6700 AH Wageningen, the Netherlands; and ‡Nutreco R&D, PO Box 220, NL-5830 AE Boxmeer, the Netherlands ABSTRACT An experiment was conducted with 768 non-cage-housed ISA Brown pullets, of which 576 hens were followed during the laying period, to investigate the separate effects of dietary energy dilution and nonstarch polysaccharides (NSP) concentration (oat hulls as NSP source) on eating behavior and feather damage. Day-old pullets were allotted to 1 of 6 dietary treatments according to a 3 × 2 factorial arrangement (3 dilution and 2 NSP levels), with 8 replicates (pens) per treatment. At 17 wk of age, pens with hens were allotted to 1 of 8 dietary treatments according to a 4 × 2 factorial arrangement (4 dilution and 2 NSP levels), with 6 replicates per treatment. Compared with 0% dilution level, feed intake of laying hens of 10, 15, and 20% dilution levels increased by 8.4% (9.5 g/hen per d), 16.5% (18.1 g/hen per d), and 20.9% (23.6 g/hen per d), respectively. The MEn intake was similar for all dilution levels. Hens fed standard-NSP laying diets had similar insoluble NSP intake for all dilution levels (9.3 g/hen per d). Insoluble NSP intake of hens fed high-

NSP laying diets increased from 15.6 g/hen per day (0% dilution) to 18.9 g/hen per day (20% dilution). Providing high- vs. standard-NSP layer diet decreased relative proventriculus contents (1.1 vs. 0.3 g/kg of BW) and increased empty gizzard weight (14.3 vs. 24.4 g/kg of BW). Hens that were fed standard-NSP diets had more feather damage compared with hens fed high-NSP diets (0.58 vs. 0.30 arbitrary units). Increasing the insoluble NSP intake resulted in decreased proventricular weight and increased gizzard weight and its contents, which are indicators of improved functioning of the gut, thereby linearly reducing feather damage. Providing diluted rearing diets increased feed intake from the first weeks of life onwards. It was hypothesized that pullets were increasingly “imprinted” on feed as pecking substrate if dilution level increased. This may decrease feather pecking and could explain the improved feather condition at 49 wk of age when 15% diluted rearing diet was fed.

Key words: feather damage, pullet, laying hen, dietary dilution, nonstarch polysaccharide 2009 Poultry Science 88:759–773 doi:10.3382/ps.2008-00194

INTRODUCTION

Feather pecking behavior was found to decrease in laying hens fed nutrient-diluted, high (in)soluble nonstarch polysaccharides (NSP)-containing diets, or roughages (Van der Lee et al., 2001; Hartini et al., 2003; Hetland et al., 2004b; Steenfeldt et al., 2007). Laying hens that are fed low nutrient density diets do compensate for this dilution by increased feed intake, resulting in a prolonged eating time (Savory, 1980; Van Krimpen et al., 2008), thereby maintaining hen performance, even in early lay (Van Krimpen et al., 2007). Our unpublished data showed that diets high in insoluble NSP content decreased eating rate (g/min) and the rate of digesta passage in the foregut, suggesting an increased satiety level of the layers. Although diets with low nutrient and high insoluble NSP contents reduced feather pecking behavior,

Feather pecking in layers is a very clear welfare problem in non-cage housing systems with a prevalence of between 40 and 80% (Blokhuis et al., 2007). Some reports hypothesized that feather pecking behavior is a substitute for normal ground pecking or feeding behavior in the absence of adequate foraging incentives (Hoffmeyer, 1969; Blokhuis, 1986). Thus, nutritional factors that increase duration of feeding behavior may positively affect feather pecking behavior in laying hens (Van Krimpen et al., 2005). ©2009 Poultry Science Association Inc. Received May 15, 2008. Accepted November 12, 2008. 1 Corresponding author: [email protected]

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the beneficial effects were small when feather pecking was already developed before diets were provided (Van Krimpen et al., 2008). Rearing conditions (wire mesh vs. soil with foraging substrate) during the first 4 wk of life might have a major influence on the subsequent development of feather pecking in laying hens (Johnsen et al., 1998). Therefore, more measures that stimulate natural behaviors are recommended to satisfy the needs of pullets in food searching and ingestion to prevent feather pecking in adult birds (Keppler et al., 1999). To validate these recommendations, an experiment was performed to investigate the effects of nutrient dilution and NSP concentration in rearing and laying diets on eating behavior and feather damage of laying hens.

MATERIALS AND METHODS Housing, Birds, and Management A total of 768 non-beak-trimmed day-old layers (ISA Brown strain) were housed in 2 climate-controlled rooms. Within each room, there are 24 floor pens (0.90 × 1.50 m). The pens were built of wire and hens could see their flock mates in other pens. Each pen contained 4 perches, a feeding trough (length of 100 cm), and 3 nipple drinkers. Sand was used as litter on the floor. A laying nest was placed outside each pen. Throughout the experiment, litter quality was maintained by adding new sand monthly. During rearing from 0 to 16 wk of age and laying from 17 to 49 wk of age, the number of birds per pen was 16 and 12, respectively. At the start of the laying period, pen weights were standardized by removing 4 birds that deviated most from the mean. Mean weight of the remaining birds was 1,475 g (SD 37). To stimulate feather pecking behavior, stocking density was higher (10.4 hens/m2) than usual in practice (9.0 hens/m2). Feed and water were provided for ad libitum consumption. Temperature was decreased each week by 2.5°C from 33°C in wk 1 to a constant value of 21°C from wk 5 onwards. At the onset of the experiment, the following light scheme for ISA Brown pullets was provided. Light was on during 22 h per day for the first 3 d, followed by a gradual reduction to 10 h per day in wk 7, and this pattern was maintained until wk 16. At 17 wk of age, light schedule was gradually extended by 1 h per week to a 16L:8D light schedule at the age of 22 wk. This photoperiod was maintained until wk 49 and lasted from 0100 to 1700 h. Health status of the hens was monitored daily.

Experimental Design At d 0, pullets were allotted to 1 of 6 dietary treatments according to a 3 × 2 factorial arrangement. The factors were dietary dilution (0, 10, and 15% dilution) and insoluble NSP concentration [124 g/kg (control) vs. 184 g/kg (high)]. These NSP contents were the average for both rearing phases. Each treatment had 8 replicates. Rearing diets in phase 1 (wk 1 to 7) and phase 2

(wk 8 to 16; Table 1) had similar MEn concentrations, with 2,630, 2,370, and 2,250 kcal/kg for the 0, 10, and 15% diluted diets, respectively. Because each of the 6 rearing diets was replicated 8 times, we randomly assigned 1 replicate from each rearing treatment at the start of the laying period to 1 of the 8 layer treatments according to a 4 × 2 factorial arrangement. The factors were dietary dilution (0, 10, 15, and 20% dilution) and insoluble NSP concentration [72 g/kg (control) vs. 115 g/kg (high); on average for the laying diets], with 6 replicates per treatment. The MEn concentrations were 2,830, 2,540, 2,390, and 2,250 kcal/ kg for the 0, 10, 15, and 20% diluted laying diets, respectively (Table 2). The experiment was comprised of 48 treatment combinations (6 treatments in the rearing period × 8 treatments in the laying period) and each treatment combination was tested in 1 pen. Dietary dilution in the standard-NSP diets was realized by adding 10, 15, or 20% sand to the control feed (0% dilution, control NSP). The high insoluble NSP diet was obtained by adding 10% whole oat hulls to the control diet at the expense of all other ingredients. Whole oat hulls were directly added in the mixer, without passing through the hammer mill. To maintain the energy concentration in the 0% diluted, high-NSP diet, extra fat was added. All feeds were fed in mash form. Ratio of MEn to all other nutrients was similar for all diets, except for ash and NSP. The nondiluted rearing and laying diets had NSP concentrations according to NRC requirements for rearing and laying hens (NRC, 1994).

Measurements Analytical Procedures. Feed was analyzed for DM, crude ash, crude fat, crude fiber, nitrogen, starch, sugars (mono- and disaccharides as glucose units), calcium, phosphorus, sodium, potassium. Neutral detergent fiber, acid detergent fiber, and acid detergent lignin were measured to obtain cellulose and hemicellulose. All samples were analyzed in duplicate. For determination of the DM content, feed was freeze-dried according to ISO method number 6496 (ISO, 1998b). After freezedrying, feed was ground to pass a 1-mm screen and kept for analysis. Air-dry feed was dried in a forced-air oven at 103°C to a constant weight according to ISO method number 6496 (ISO, 1998b). Kjeldahl nitrogen content was measured according to ISO method number 5983 (ISO, 1997) in fresh feed. Crude protein content was calculated as nitrogen × 6.25. Crude fat content was determined after acid hydrolysis according to ISO method number 6492 (ISO, 1999). For determining crude ash content, samples were incinerated at 550°C in a muffle furnace according to ISO method number 5984 (ISO, 2002). The starch content was analyzed enzymatically as described by Brunt (1993). Reducing sugars were extracted from the feed samples, using 40% ethanol, and determined as described by Suárez et al. (2006). Contents of calcium, phosphorus, sodium, and

Ingredient   Wheat   Barley   Soybean meal extracted (CF